Friday 13 April 2012 16.35 EDT
First published on Friday 13 April 2012 16.35 EDT

The producer of ITV's £12m Titanic mini-series has admitted the show's nonlinear storytelling, which sees the ship hit the iceberg in each episode, may have put viewers off the Julian Fellowes-scripted drama that has foundered in the ratings.

Nigel Stafford-Clark said it was his idea to have a narrative moving back and forth in time, as a fresh approach to a well-known story. The four-parter, which concludes on Sunday night, launched successfully with 7.4 million viewers, but had fallen to 3.5 million by the third instalment – fewer than saw a show marking comedian Des O'Connor's 80th birthday which preceded it on ITV1. Stafford-Clark, a 30-year TV industry veteran with producer credits including Peter Kosminsky's Northern Ireland docu-drama Shoot to Kill and the same director's Bosnian war drama Warriors, said he was proud of Titanic, which focuses on different classes aboard the doomed liner in each episode. He had previously enjoyed critical and ratings success for a similar fresh approach with BBC1's 2005 Bleak House adaptation, which broke up the Dickens story into TV soap-sized half hour episodes. But he admitted Titanic had failed to woo viewers in the same way. "I have to accept that people have found it hard to get around. In that sense I am responsible," he said.

He also defended Fellowes' work on the drama. "The scripts were very good. Julian is not in any way responsible for this. He wrote the scripts over 18 months to two years, it was not done in a hurry. The series was sold off the back of the script."

Simon Vaughan, the executive producer who first pitched the idea of a TV drama to mark the 100th anniversary of the Titanic sinking and raised co-production funding around the world, said when he began the project five years ago he had no idea there would be so much competition.

As well as the re-release of James Cameron's blockbuster movie in 3D, the ITV drama has had to compete with a glut of TV documentaries, including BBC1's Titanic with Len Goodman and Channel 5's Nazi Titanic: Revealed.

However, the ITV Studios-produced mini-series looks like being a commercial success, having sold to nearly 100 countries, with the DVD released in the UK on Monday. "As a piece of business it's been exceptional, financially extremely valuable to everyone involved," Vaughan said.

An ITV spokesman said: "The 100th anniversary of the Titanic sinking was marked with programmes from all the channels, and we are proud to have offered our audience a new drama that had real scale and ambition."